Genetic Enhancements of Color Qualia

The fourth color opsin for these animals lies in the ultraviolet.

Hmm, but my understanding is that humans who are natural tetrachromats see more colors in the yellow-red part of the spectrum. And humans already can see UV light a little, but the thing that stops this from being visible is actually the lens, which blocks UV light normally to protect our eyes. So what I know suggests that even if we could change our cones we'd still fail to see UV light.

[-]TerriLeaf1mo30

Hmm, but my understanding is that humans who are natural tetrachromats see more colors in the yellow-red part of the spectrum

There is genetic evidence that some people might be natural tetrachromats, though as far as I know only one case has been confirmed, sort of. If this is true these people would have an additional Q type cone cell, with responsivity in the visible spectrum (so they don't see UV). The mean responsivity of Q cells is in between M and L cells with heavy overlaps, so many of these new color qualia are also inaccessible.

And humans already can see UV light a little, but the thing that stops this from being visible is actually the lens, which blocks UV light normally to protect our eyes

UV-A is not stopped by the lens and can reach the retina.

[-]Gavin Runeblade2mo10

" The fourth color opsin for these animals lies in the ultraviolet. For humans such a protein must be carefully picked among existing ones (or else designed anew) since the human eye naturally blocks UV light. UV-A (320-400 nm) is likely the best candidate as a large part of it reaches the retina and there are animal uv opsins with mean responsivity at around 370 nm. "

How does this compare to those humans who are naturally tetrachromate? Do they see ultraviolet as well, or something else? And why select something other than what they have which clearly works with human brains and eyes?

[-]TerriLeaf1mo20

I think it'd be more interesting to expand the frequencies that humans can see rather than just add a new color among the current visible spectrum. Many birds and flowers possess features with colors in the UV which we cannot appreciate right now. Also, squeezing more peaks inside the visible spectrum without expanding it might be difficult if we also want to keep these curves decetly separated.

Color Gamut Expansion

LMS color space represents the response of the three cone cells of the human eye, named after the wavelength of their relative peak responsivity (long, medium and short). Proteins called opsins are mostly responsible for this response.

Overlaps between these peaks makes resolving colors difficult, this is particularly problematic for M cones since their wavelength lies in between the other two.

M and L spectra share a large area making experience of some intermediate and pure colors virtually impossible

These poorly designed absorption curves make about 30% of our gamut color space completely inaccessible under normal conditions.

Large area of the theoretical LMS human color triangle is "polluted" by sympathetic activation of different cone cells

To address this issue new opsin proteins must be generated and used to replace the current ones. These new proteins must possess curves that are well separated with means equally spaced between them. To design these new proteins techniques like directed evolution can be employed, alternatively a suitable alternative can be searched among their biological homologous.

In a recent study scientists were able to make a machine (a sort of advanced laser display) that can, to a certain degree, selectively stimulate individual cone cells within the retina; test subjects confirmed they could experience a novel color quale. Refining the responsivity curves of our opsin proteins would have the same effect, effectively adding up to a million new colors to our everyday experience.

Unfortunately germline engineering is necessary to implement this fix, as virtually all the cone cells in both our eyes need to be modified for this to work. Tissue engineering and retina transplant may make this genemod available to baseline humans in the medium-term future.

Dimensional Expansion

A completely new color can be added to our vision by adding a new opsin gene to our current set, making us tetrachromats. The common ancestor of vertebrates was a tetrachromat as are birds and other modern animals, with four distinct channels for conveying chromatic information, their color space is 4D.

Tetrachromats have an expanded LMSV color space in the shape of a tetrahedron

The fourth color opsin for these animals lies in the ultraviolet. For humans such a protein must be carefully picked among existing ones (or else designed anew) since the human eye naturally blocks UV light. UV-A (320-400 nm) is likely the best candidate as a large part of it reaches the retina and there are animal uv opsins with mean responsivity at around 370 nm.

Gene therapy protocols have already been explored to add a new color in animal vision with successful results, while, to my knowledge, germline engineering has not been explored for this type of editing.

Hypothetical "optimal" spectra of engineered human opsins, including an additional uv opsin

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Genetic Enhancements of Color Qualia

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Color Gamut Expansion

Dimensional Expansion

References